Geographic Range

Swift foxes originally ranged from the plains of western Canada and across the Great Plains of North America to Texas. Swift foxes disappeared entirely from Canada in the 1930s, but have been reintroduced there. At present there are a few scattered populations of swift foxes in the Great Plains of the U.S. and in western Canada. The largest population is in Colorado, Kansas, New Mexico, and Wyoming, where the species is stable. There are currently approximately only 350 individuals located in Southeast Alberta and Southwest Saskatchewan.

Physical Description

The swift fox is the smallest of the wild dogs in North America. Adults weigh between 2 and 3 kilograms and are approximately 30 cm tall and 80 cm long. They are about the size of a domestic cat. Males and females look similar except that males are slightly larger. The fur of V. velox is light grey with orange-tan coloring on the sides and legs. The throat, chest, underside and inside of the ears are creamy white. The tail is bushy and marked with black at the tip. There are also black patches on either side of the snout.

Reproduction

Male swift foxes mature and mate at one year, while females may wait until their second year before breeding. The breeding season for individuals in Canada begins in March. The gestation period is 50-60 days and pups are born in mid-May. The breeding season for individuals farther south in the United States begins in late December, early January, with pups born in March and early April.
Swift foxes have only one litter annually, with a litter size ranging anywhere from 2 to 6.

Pups are born in the underground den and typically remain there for about one month. After birth, the eyes and ears of the pups remain closed for 10 to 15 days, thus leaving them dependent on the mother for food and protection. Pups are weaned when 6 to 7 weeks old but usually remain with the mother and father until the fall.

Behavior

The swift fox is indeed rather swift, reaching speeds of over 50 km/h. Their speed helps them catch food and avoid predators. Swift foxes also avoid predators by seeking shelter in burrows. Their dens are burrows underground, usually 2-4 meters in length with 4 entrances. Vulpes velox is mainly a nocturnal species. Daytime activities are confined to dens and vary seasonally. In winter, foxes may sun bathe during the warm midday period, while in summer they only spend early evenings and nighttime above ground.

Communication and Perception

Food Habits

The diet of the swift fox varies seasonally, depending on what is available. It typically eats whatever live prey it can catch. Its diet includes small mammals, birds, reptiles, amphibians, fish, insects, but also includes berries and grasses.

Economic Importance for Humans: Positive

Economic Importance for Humans: Negative

The cost of captive breeding programs and monitoring after reintroduction can often be high.

Conservation Status

The swift fox is a severely endangered species. It has faced habitat losses due to agricultural, industrial and urban development. Hundreds of swift foxes were killed accidentally during the early 1930s from predator control programs aimed at removing wolves, coyotes, and ground squirrels from prairies. In 1978, the species was declared extirpated in Canada.
There are currently populations of swift foxes in the U.S. ranging from South Dakota to Texas. However, the population is stable only in the central part of the range. Reintroduction programs in Western Canada have established small populations in southeast Alberta and southwest Saskatchewan, totaling 350 foxes. The current goal of reintroduction programs in Canada is to establish a viable, self-sustaining population distributed across the prairies and to remove the species from the endangered category by the year 2000.

Several things can be done to try to prevent further loss of and to encourage repopulation of swift foxes. Preserving the habitats of the foxes is crucial. Also, captive breeding could help increase the number of swift foxes. Reintroduction programs, like the ones in western Canada, may also be successful in restoring the swift fox to its natural habitat. However, a large number of reintroduced individuals do not survive their first year in the wild for one reason or another. Therefore, populations must be monitored and protected from human harm. Even though it is illegal to kill swift foxes, they are sometimes mistaken as coyotes and killed.

Other Comments

There is ongoing controversy over whether swift foxes should be divided into two separate species, swift foxes (Vulpes velox) and kit foxes (Vulpes macrotis). Protein electrophoresis data and morphometric analyses have suggested that the species Vulpes velox contains both swift foxes (Vulpes velox velox) and kit foxes (Vulpes macrotis) (Ewer 1973; Clutton-Brock et al. 1976; Dragoo et al. 1990; Wozencraft 1993). However, other morphometric analyses (Stromberg and Boyce 1986) and analyses based on mitochondrial DNA (Mercure et al. 1993) have suggested that swift foxes and kit foxes are indeed distinct species. In fact, the study by Mercure et al. (1993) demostrated that swift foxes and kit foxes are as closely related to Arctic foxes (Vulpes lagopus) as they are to one another. In any case, swift foxes and kit foxes are ecologically and morphologically similar taxonomic groups. The former is distributed to the east of the Rocky Mountains, and the latter is distributed to the west. There is a narrow hybrid zone between the two populations in eastern New Mexico and western Texas (Mercure et al. 1993). (Clutton-Brock, et al., 1976; Dragoo, et al., 1990; Ewer, 1973; List and Cypher, 2004; Mercure, et al., 1993; Moehrenschlager and Sovada, 2004; Stromberg and Boyce, 1986; Wozencraft, 1993)

Contributors

Karen Resmer (author), University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carrion

flesh of dead animals.

chemical

uses smells or other chemicals to communicate

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

omnivore

an animal that mainly eats all kinds of things, including plants and animals

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

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The Animal Diversity Web is an educational resource written largely by and for college students. ADW doesn't cover all species in the world, nor does it include all the latest scientific information about organisms we describe. Though we edit our accounts for accuracy, we cannot guarantee all information in those accounts. While ADW staff and contributors provide references to books and websites that we believe are reputable, we cannot necessarily endorse the contents of references beyond our control.

This material is based upon work supported by the
National Science Foundation
Grants DRL 0089283, DRL 0628151, DUE 0633095, DRL 0918590, and DUE 1122742. Additional support has come from the Marisla Foundation, UM College of Literature, Science, and the Arts, Museum of Zoology, and Information and Technology Services.